As one of the information sources of an automotive electronic control system, the general purpose pressure sensor for an automobile is a critical part of the automotive electronic control system, and also is one of the core contents of the research on the technical field of automotive electronics. The general pressure sensors for an automobile are mainly used for the control of pressure measurement of parts such as brake systems, automatic transmissions, air-conditioning systems, suspension systems, engine oil pressure, power switching transmission systems, engine direct injection pressure, LPG and CNG systems and the like in automobiles.
In the 1980s, traditional automotive high pressure sensors used thick film ceramic technique. With the development of many years, the cost for manufacturing ceramic core has been reduced significantly these days and the price meets the requirements of automotive application. However, due to its high brittleness, ceramic materials are poor in resistance to overload of liquid pressure impact (generally with a overload capacity of only 1.5˜2 times of static pressure), and poor in vibration resistance, low in reliability and low in output sensitivity (2 mV/V), so that it is confronted with elimination as it could not meet the development needs of the pressure measurement in automobiles.
In the 1990s, there also appeared automotive high pressure sensors using strain technology, which still remained low cost property for core manufacturing, but solved the problem of poor vibration resistance of the thick film ceramic and improved the ability to resist the pressure impact overload at the same time. However, since the structural principle of the sensor used an adhesive metal strain technology, the fatigue of the organic adhesive resulted in a shorter lifetime of the whole sensor, and measuring accuracy degraded with the time of usage due to creep of the adhesive, and meanwhile, the sensitivity output was still very low.
Recently, Measurement Specialties Inc. of America and Sensata of America have made improvements for the above described strain technology by replacing the adhesive strain gage technology with high temperature glass powder sintered silicon strain gage technology. Despite the slight increase of the core manufacturing cost, it solves the problem of lifetime and measuring accuracy of the sensor which varies with time, and the utilization of silicon strain gage increases sensitivity output significantly at the same time. However, in the glass powder sintering process, the area is relatively large due to the thinness of the glass powder layer, for a glass material which is relatively fragile, when it is subjected to rapid pressure overload impact and temperature impact, rupture will occur in the sintered glass layer, and its pressure overload impact resistance generally still remains only two times, and the operating temperature range is only −20˜80° C., thus it can not meet operating requirements of the automobile level in many aspects. Also, at the later stage, the disadvantage of above described strain mode was solved by sputter thin film mode general pressure sensor which is derived from the strain mode. The operating temperature region could also meet requirements of the automobile level, and the sensitivity output could reach 5 mV/V and the resistance of impact pressure overloads two times. However, due to its relatively high manufacturing cost, it can not be popularized in automotive application in a wide range.
Companies such as KELLER of Europe and Honeywell of America use MEMS monocrystalline silicon sensitive element, where the sensitivity output could be up to 20 mV/V and the resistance of impact pressure overloads 3 times, on the premise of satisfying the application of automobile level. Although a relative batch manufacturing of sensitive elements with low cost is achieved by utilizing semiconductor MEMS process, because the international general design of the monocrystalline silicon general pressure sensor chip is a structure where the rear surface supports the chip and the front surface bears pressure, among them a complex isolating oil-filled welding technique is needed to meet the compatibility requirement of the measuring medium. Thus the manufacturing cost of the products is increased significantly, and therefore it can not be popularized in automotive applications in a wide range.